A rotary encoder is an important sensor commonly used in closed loop velocity control and positioning applications within industrial applications, for example, in plants for paper or steel making in which the rotary encoder may be arranged to detect rotary movement of a machine shaft. In general, rotary encoders include a detector part which detects rotary motion and generates a signal corresponding to the detected angular position change. Different values, such as angular velocity and number of revolutions may be derived from the signal. The rotary encoders further include a mechanism, such as a bearing, for attaching the rotary encoder to a shaft of a machine whose movement is to be detected as well as a mechanism for attaching a casing of the rotary encoder to a casing of the machine.
There are several different types of rotary encoders, for example, optoelectrical encoders as described in European Patent No. 1 480 344. This type of encoder includes an encoding disc that has an optically readable pattern. There are also other types of rotary encoders based on other measurement principles. These encoders include, for example, magnetic encoders, inductive encoders, capacitive encoder, etc.
One problem related to rotary encoders is that the rotary encoders are used in environments which cause different types of wear to the rotary encoder. Due to the wear that the rotary encoder is subjected to the overall condition of the rotary encoder degrades which in turn may lead to malfunctioning of the rotary encoder.
Another factor which may influence negatively on the overall condition of the rotary encoder is the quality of the installation of the rotary encoder, for instance, the alignment of the rotary encoder when the rotary encoder is installed in the machine.
A faulty rotary encoder could lead to unscheduled stops of machines or plants for service or replacement of parts. This is disadvantageous since it leads to costly drops in production.
It is conventional to monitor the condition of rotary encoders. The optical rotary encoder described in European Patent No. 1 480 344 includes a circuit that provides a warning signal when the optical disc of the rotary encoder is contaminated. A user is then informed that the encoder needs service. However, although beneficial, the rotary encoder described in European Patent No. 1 480 344 does not provide the user with information about the quality of the installation of the rotary encoder or about the environment in which the encoder is located.